Embodiments described herein relate to a method for pipetting a blood plasma component and a red blood cell component, etc. with blood analysis or blood test which is carried out in an automatic pipetting apparatus.
Various kinds of tests are conducted for a blood sample collected from a human body. For example, in a blood type test, as shown in FIG. 10, the collected blood sample 10 is put into a test tube 12 and is then separated into a blood plasma component 14 and a red blood cell component 16 by centrifugation. Practically, a small quantity of a white blood cell component 18 appears between the blood plasma component 14 and the red blood cell component 16. Since the white blood cell component is not relevant to the following description, it is omitted from the other drawings.
A well known method for pipetting a blood sample which is carried out in a conventional apparatus comprises mainly two steps: a step for pipetting blood plasma and a step for pipetting red blood cells. In the blood plasma pipetting step, the blood plasma 14 is aspirated by a nozzle tip 20 and is then separately piperred into a plurality of recipient containers 22 in a predetermined volume. In the red blood cell pipetting step, the red blood cell component 16 is aspirated by the same nozzle tip 20 and is then pipetted into a non-illustrated diluting container to be mixed with a diluent, whereupon the diluted solution of red blood cell component 16 is again aspirated by the nozzle tip 20 and is then pipetted into a plurality of another recipient containers 24, respectively in a predetermined volume.
Blood type testing reagents (a reagent for the blood plasma component, and a reagent for the red blood cell component) are introduced into the recipient containers 22, 24, respectively.
Then, these recipient containers 22, 24 are moved to an agglutination testing apparatus, where agglutination tests of the blood sample in the containers are conducted optically. From the results of these measurements, the blood types, such as A, B, O, AB and RH, of the blood sample are determined.
However, the red blood cell component is a high viscosity liquid (or a gel-like substance), so a quick pipetting of the red blood cell component cannot be achieved by the conventional pipetting method. Since the red blood cell component can not be aspirated smoothly through an orifice at a distal end of the nozzle tip due to high viscosity of the red blood cell component, it takes a long time until an amount of red blood cell component to be aspirated reaches to a predetermined volume. Consequently, a quick pipetting operation can not be conducted by using the conventional pipetting apparatus.
Further, in the conventional pipetting apparatus, contamination between blood samples has been prevented by thoroughly cleaning the nozzle tip for each sample, without exchanging the nozzle tip with a new one for each blood sample. Since such cleaning operation is labor-intensive and complex, it has been long desired to use a disposable nozzle tip.